The exhaust gas emitted from an internal combustion engine, is a heterogeneous mixture that may contain gaseous emissions such as carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NOx”) as well as condensed phase materials (liquids and solids) that constitute particulate matter (“PM”). Catalyst compositions typically disposed on catalyst supports or substrates are provided in an engine exhaust system to convert certain, or all of these exhaust constituents into non-regulated exhaust gas components.
In an exhaust treatment technology, there are several known filter structures used that have displayed effectiveness in removing the particulate matter from the exhaust gas such as ceramic honeycomb wall flow filters, wound or packed fiber filters, open cell foams, sintered metal fibers, etc. Ceramic wall flow filters have experienced significant acceptance in automotive applications.
Typically, a particulate filter is disposed along the exhaust stream to filter the particulates from the exhaust. Over time, the particulate filter may become full and regeneration is required to remove any trapped particulates. Regeneration of a particulate filter in vehicle applications is typically automatic and is controlled by an engine or other controller based on signals generated by engine and exhaust system sensors. The regeneration event involves increasing the temperature of the particulate filter to levels that are often above 600° C. in order to burn the accumulated particulates to enable the continuation of the filtering process.
There are drawbacks associated with the regeneration process. These include the fuel consumption required to regenerate the particulate filter and exhaust emissions that are created by the regeneration process (e.g., upward adjustment factors (UAF) for NOx and HC).
Accordingly, it is desirable to provide an apparatus and method for regenerating a particulate filter that will result in reduced fuel consumption and near zero exhaust emission during particulate filter regeneration.